Form_remote_tag and csv download?

Good morning! I have a case where I need to build a csv file from my
model and allow a user to download/save that file. I’ve got this all
working with non-Ajax forms, but the generation of the csv file can take
quite a bit of time, so I want to provide a busy indicator for my user.
So I tried the following in my view:

<% form_remote_tag ( :url =>{:action => ‘all_open’},
:update => “test” ,
:before => “Element.show(‘busy_indicator’)”,
:complete => “Element.hide(‘busy_indicator’)”) do %>
<%= submit_tag ‘Save Report’, {:name => ‘save_report’} %>
<% end %>

which only updates the “test” div, as I expected (but this isn’t what I
want since the data is already displayed in a pretty table on the page).
I googled and found suggestions to try send_file, but since I’m building
my csv from a model and don’t want to save the file server-side, this
won’t work. I also found Can't download files with send_data or send_file - Rails - Ruby-Forum, but
I need the busy indicator so user’s don’t mash the save button
incessantly. Is there any way at all to pop up my busy_indicator and
still start the file download?

Any help/advice would be greatly appreciated (especially if it’s
quick…this is the last thing I need to fix before deploying the
app:)).

Thanks in advance!

-Chris